This invention relates to soil probes and particularly to a water jet sediment probe to determine, for example, the thickness of sand and other sediments on a beach overlying bedrock or the depth and type of sediment beneath a seafloor, etc.
Frequently, it is necessary to determine the depth of sand or various types of sediment on a beach or the seafloor in the vicinity of a beach for purposes of installing piles or other devices in the construction of piers and causeways and other structures. Also, it may be desirable to know the types and depths of sediment on a seafloor prior to installation of propellant embedded anchors and the like. An experienced operator while spudding a probe pipe into sediment can estimate the types of sediment being penetrated by feeling the vibrations transmitted from the lower tip of the probe pipe as it passes through the sediment layers.
A sediment probe using a water jet, also known as a wash pipe, generally consists of a rigid length of metal pipe, a flexible hose, and a source of water under pressure (from a water pump), Water being expelled under pressure from the end of the metal pipe or a jet nozzle at the end of the metal pipe operates to displace sediment or soil as it is being spudded (i.e., pushed) into the sediment by an operator. Soil is liquified at the point of entry and remains liquified ("quick") as long as water is continued to be pumped into the hole from the probe. The length of the metal pipe is limited by the operator's strength and height. A ten foot length of pipe is about the maximum practical limit for one person to work with and handle without assistance. A twenty-foot length of pipe can be used if guy lines are used to hold the pipe vertical, but such lengths require at least three guy line tenders in addition to the operator (spudder). Also, it is impossible to bore a deep hole using several sections of short pipe connected one at a time, because when water circulation is interrupted to make a pipe connection the sand, gravel, pebbles and rocks in the loose sediment will resettle and block water circulation when the pump is restarted, thus preventing further penetration. In addition, the resettled sediments may prevent or make it difficult to remove the pipe from the hole. No simple and satisfactory prior system has been found whereby one person working alone can bore a deep hole, such as 30 feet or deeper, due to the difficulty for the spudder to handle a probe pipe over 10 feet in length.